polarization in relativistic heavy ion collisions

Jiaxing Zhao; Baoyi Chen

doi:10.1140/epjc/s10052-024-13264-w

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2024) 84: 875
https://doi.org/10.1140/epjc/s10052-024-13264-w

Regular Article - Theoretical Physics

$J / ψ$ $J/\psi$ polarization in relativistic heavy ion collisions

Jiaxing Zhao¹^a and Baoyi Chen²

¹ SUBATECH, Université de Nantes, IMT Atlantique, IN2P3/CNRS, 4 rue Alfred Kastler, 44307, Nantes cedex 3, France
² Department of Physics, Tianjin University, 300354, Tianjin, China

^a zhao-jx15@tsinghua.org.cn

Received: 16 January 2024
Accepted: 20 August 2024
Published online: 30 August 2024

Abstract

Understanding the polarization property of $J / ψ$ $J/\psi$ is critical to constrain its production mechanism. In addition, the polarization of $J / ψ$ $J/\psi$ can reveal the impact of strong electromagnetic and vorticity fields in relativistic heavy ion collisions. In this study, we analyzed the yield and polarization of $J / ψ$ $J/\psi$ in relativistic heavy ion collisions at different centrality and transverse momentum regions, using three different reference frames: the Collins–Soper frame, the helicity frame, and the event plane frame. The polarization of initially produced $J / ψ$ $J/\psi$ is determined by the NRQCD calculation and is similar to that of pp collisions. However, both unpolarization and transverse polarization are considered for the regenerated $J / ψ$ $J/\psi$ . Our results indicate that the polarization at high $p_{T}$ $$p_T$$ is similar to that observed in pp collisions. However, at low $p_{T}$ $$p_T$$ , where regenerated $J / ψ$ $J/\psi$ dominates, it is likely that the polarized charm quarks in the rotational QGP medium are responsible for this phenomenon. Our study supplies a baseline for future research on the effects of strong electromagnetic and vorticity fields on $J / ψ$ $J/\psi$ polarization.

© The Author(s) 2024

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.